Math Problem Statement

lim[\displaylines(21x2)+(1x1){\displaylines\left(\frac{2}{1-x^2}\right)+\left(\frac{1}{x-1}\right)\\ }

Solution

To evaluate the limit:

limx1(21x2+1x1)\lim_{x \to 1} \left( \frac{2}{1-x^2} + \frac{1}{x-1} \right)

First, simplify each term.

Step 1: Simplify the first term

The expression 21x2\frac{2}{1 - x^2} can be factored using the difference of squares formula:

1x2=(1x)(1+x)1 - x^2 = (1 - x)(1 + x)

Thus,

21x2=2(1x)(1+x)\frac{2}{1 - x^2} = \frac{2}{(1 - x)(1 + x)}

Step 2: Combine the two terms

Now we rewrite the full expression:

2(1x)(1+x)+1x1\frac{2}{(1 - x)(1 + x)} + \frac{1}{x - 1}

Since x1=(1x)x - 1 = -(1 - x), the second term becomes:

1x1=11x\frac{1}{x - 1} = -\frac{1}{1 - x}

Now the expression becomes:

2(1x)(1+x)11x\frac{2}{(1 - x)(1 + x)} - \frac{1}{1 - x}

Step 3: Find a common denominator

The common denominator for the two terms is (1x)(1+x)(1 - x)(1 + x). So we rewrite the second term:

11x=1(1+x)(1x)(1+x)=(1+x)(1x)(1+x)\frac{-1}{1 - x} = \frac{-1(1 + x)}{(1 - x)(1 + x)} = \frac{-(1 + x)}{(1 - x)(1 + x)}

Now, combine both terms:

2(1+x)(1x)(1+x)=21x(1x)(1+x)=1x(1x)(1+x)\frac{2 - (1 + x)}{(1 - x)(1 + x)} = \frac{2 - 1 - x}{(1 - x)(1 + x)} = \frac{1 - x}{(1 - x)(1 + x)}

Step 4: Simplify the expression

The numerator and one factor of the denominator cancel out:

1x(1x)(1+x)=11+x\frac{1 - x}{(1 - x)(1 + x)} = \frac{1}{1 + x}

Step 5: Evaluate the limit

Now, take the limit as x1x \to 1:

limx111+x=11+1=12\lim_{x \to 1} \frac{1}{1 + x} = \frac{1}{1 + 1} = \frac{1}{2}

Thus, the value of the limit is:

12\boxed{\frac{1}{2}}


Would you like further details or have any questions?
Here are five related questions you might find interesting:

  1. What happens if we try to evaluate this limit without factoring?
  2. How does L'Hôpital's Rule apply to limits involving indeterminate forms?
  3. How can we evaluate limits at infinity for similar expressions?
  4. Can we use series expansions to solve this limit?
  5. How do we deal with limits involving trigonometric identities?

Tip: Always check if you can factor expressions to simplify complex limits!

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Math Problem Analysis

Mathematical Concepts

Limits
Algebra
Factoring
Indeterminate Forms

Formulas

Difference of squares: 1 - x^2 = (1 - x)(1 + x)
Limit of a rational expression as x approaches a value

Theorems

L'Hôpital's Rule (implicitly applicable)
Factoring techniques

Suitable Grade Level

Grades 11-12